JP2005006768A - Electronic endoscope equipment and signal processor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electronic endoscope equipment which provides excellent images with less noise under accurately set color balance. <P>SOLUTION: A light source unit 5 successively irradiates an object 7 with illumination light having different wavelength bands. An electronic endoscope 2 is provided with a CCD 20 for picking up the image of the object 7 for each wavelength band of the emitted illumination light. Color balance correction circuits 35 and 36 amplify signals corresponding to the object 7 outputted from the CCD 20 for each wavelength band. A CPU 40, a sampling circuit 41 and an exposure time control circuit 43 act as an exposure time setting means for setting the exposure time of the CCD 20 for each wavelength band. Further, the CPU 40 sets the amplification factor of the color balance correction circuits 35 and 36 for each wavelength band on the basis of the signals corresponding to the object 7 whose image is picked up by the CCD 20 by the exposure time set by the exposure time setting means. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electronic endoscope apparatus that obtains an image by an image sensor that captures a subject image by accumulating electric charges, and a signal processing apparatus used in the electronic endoscope apparatus.
[0002]
[Prior art]
Conventionally, by inserting a scope into a body cavity, the gastrointestinal tract of the esophagus, stomach, small intestine, large intestine, etc. and the trachea of the lung etc. are observed, and various treatment tools are inserted using the treatment instrument channel as necessary. Electronic endoscope devices that can perform treatment are widely used.
[0003]
As an electronic endoscope, a rotary optical filter is provided in the light source device, and light such as red, green, and blue is sequentially emitted from the light source device to the subject. 2. Description of the Related Art There are frame sequential electronic endoscope apparatuses that receive light, perform signal processing in a signal processing apparatus, and output the result as a color image to a display apparatus.
[0004]
In this field sequential type electronic endoscope, there are individual differences in the wavelength characteristics of the optical filter and the spectral sensitivity characteristics of the image sensor. Therefore, in general electronic endoscope apparatuses, white balance using an electronic circuit is used. Adjustments have been made.
[0005]
The white balance is adjusted by pressing a switch for setting the white balance in a state where a white object is imaged. The white balance adjustment circuit adjusts the color balance by adjusting the amplitude of the B signal and the R signal with respect to the G signal to be a predetermined ratio when the switch is pressed. In the case of an analog circuit, this adjustment is generally performed by comparing the output of each signal with a comparator and adjusting the amplification factor little by little so as to converge to a predetermined color. However, in this case, it takes time because an image for a large number of frames is required until the accurate white balance adjustment is completed.
[0006]
On the other hand, when the color balance is adjusted by a digital circuit, each color signal in one frame is sampled, and the amplification factor of the B signal and R signal is directly calculated by the CPU or the like from the intensity ratio, and the digital multiplier is set. Often used to amplify each signal. In this case, it takes no long time to adjust the white balance.
[0007]
In diagnosis using an electronic endoscope apparatus, auto-fluorescence observation using auto-fluorescence of living tissue has begun in addition to normal observation in which a color image similar to that seen with the naked eye is displayed on a monitor.
[0008]
In autofluorescence observation, diagnosis is performed using the fact that the spectrum of autofluorescence emitted from a living tissue when ultraviolet to blue excitation light is applied to the living tissue differs between a normal mucosa and a tumor. The autofluorescence image is assigned a different color and displayed on the monitor together with the reflected light image reflected back from the living tissue so that the lesioned part can be clearly recognized. At this time, the wavelength of the irradiated light is limited so that the spectral distribution becomes discrete in each wavelength band by using a narrow band optical filter (see, for example, Patent Document 1).
[0009]
Further, in the conventional electronic endoscope apparatus, it is common to adjust the color balance with reference to a white object (see, for example, Patent Document 2). However, as an electronic endoscope apparatus, autofluorescence observation is used. Sometimes, any patient can observe a lesion in a certain color tone by adjusting the color balance based on the color of the normal mucous membrane of the patient.
[0010]
[Patent Document 1]
JP 2002-95635 A (page 2-7, FIG. 1-33)
[0011]
[Patent Document 2]
JP-A-2002-336196 (page 3-9, FIG. 1-13)
[0012]
[Problems to be solved by the invention]
In such a conventional electronic endoscope apparatus, the amplification factor of the amplifier of the signal processing apparatus is adjusted for each color (for each wavelength band) in order to adjust the color balance. For this reason, when there is little difference in the amplification factor between the colors, there was not much problem. However, when the difference in amplification factor between the colors was large, there was a lot of noise in the color component with a high amplification factor of the image. There are things.
[0013]
In particular, in the case of an electronic endoscope apparatus for fluorescence observation, the difference in the brightness of the fluorescence emitted from the mucous membrane of the patient is large depending on the patient, and in order to correct the difference, the difference in the amplification factor between the colors is greatly increased. There is a possibility that the image becomes noticeable with noise.
[0014]
In addition, since the fluorescence is very weak, it is necessary to reduce the amount of irradiation light at the time of acquiring the reflected light image as compared with the case of irradiation with the excitation light. For this reason, since the transmission wavelength band of the filter was narrowed or the transmittance was lowered, wavelength errors at the time of manufacturing the optical filter are likely to occur, and the influence on the color of the image may be relatively large. .
[0015]
For example, when a 10 nm error occurs in a filter having a transmission band with a half width of 100 nm, the transmitted light intensity error is about 10%. However, when a 10 nm error occurs in a filter with a half width of 20 nm, 50%. % Transmitted light intensity error. As a result, when adjusting the color balance, the difference in the amplification factor between the colors tends to be large, and there is a high possibility that the image will be noisy.
[0016]
In the case of an endoscope apparatus provided with an electronic shutter, it is possible to adjust the color by controlling the exposure time. However, in the case of an endoscope apparatus that requires light shielding by a rotary filter plate or the like, the electrically set exposure time and the amount of exposure incident on the image sensor do not have a simple proportional relationship. This is because the light beam crossing the rotary filter is not completely concentrated at one point but has a certain area.
[0017]
FIG. 11 is a graph showing the relationship between the exposure amount of the rotary filter (when the electronic shutter is not used) and time, and FIG. 12 is a graph showing the relationship between the exposure amount of the rotary filter and the exposure time. is there.
[0018]
The relationship between the exposure amount and the time when one filter in the rotary filter is inserted into the light beam is ideally in the state shown by the broken line 91 shown in FIG. 11, but actually the solid line shown in FIG. The state shown in 92 is obtained.
[0019]
Further, in FIG. 11, if the electric charge is swept out by using the electronic shutter at the time A and the exposure period ends and the light shielding period starts at the time B, the exposure time becomes the time A to B in FIG. . At this time, the relationship between the exposure time and the exposure dose is as shown in FIG. In FIG. 12, ideally, it is preferable that the exposure time and the exposure amount are proportional as indicated by a broken line 93, but actually, the relationship is complicated as indicated by a solid line 94. Furthermore, the characteristics of the solid line 92 shown in FIG. 11 and the solid line 94 shown in FIG. 12 differ depending on the types of endoscopes and light source devices, individual variations, and the like. For this reason, it has been difficult for an electronic endoscope apparatus using a rotary filter to set a precise color balance by simply adjusting the exposure time.
[0020]
The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an endoscope apparatus that can produce a better image with less noise under a precisely set color balance.
[0021]
[Means for Solving the Problems]
In order to achieve the above object, an endoscope apparatus according to claim 1, wherein a light source device that sequentially irradiates illumination light having different wavelength bands with respect to a subject, and the wavelength band of illumination light emitted to the subject. An endoscope provided with an imaging device for imaging, amplification means for amplifying a signal corresponding to a subject output from the imaging device for each wavelength band, and setting an exposure time of the imaging device for each wavelength band And an amplification factor for setting the amplification factor of the amplification unit for each wavelength band based on a signal corresponding to the subject imaged by the imaging device with the exposure time set by the exposure time setting unit. And setting means.
[0022]
An endoscope apparatus according to claim 2 is the electronic endoscope apparatus according to claim 1, wherein a display device for color-displaying an image according to the signal amplified by the amplification means, Color balance setting instructing means for instructing color balance adjustment of video displayed on the display device, and the exposure time setting means is output by the imaging device based on an instruction from the color balance setting instructing means An exposure time for each wavelength band is set based on a video signal.
[0023]
The endoscope apparatus according to claim 3 is the electronic endoscope apparatus according to claim 1 or 2, wherein the light source device supplies excitation light for exciting the subject to the subject, The imaging device is characterized by imaging fluorescence from a subject.
[0024]
The endoscope apparatus according to claim 4 is the electronic endoscope apparatus according to claim 1 or 2, wherein the light source device applies illumination light in a wavelength band having a discrete spectral distribution to a subject. It is characterized by being supplied to.
[0025]
The signal processing device according to claim 5 is a signal processing device that processes a signal corresponding to a subject output from an endoscope including an imaging device, and sequentially irradiates the subject and has different wavelength bands. Amplifying means for amplifying a signal corresponding to a subject imaged by the imaging device for each wavelength band of illumination light for each wavelength band; and exposure time setting means for setting an exposure time of the imaging device for each wavelength band; An amplification factor setting means for setting the amplification factor of the amplification unit for each wavelength band based on a signal corresponding to the subject imaged by the imaging device with the exposure time set by the exposure time setting unit; It is characterized by that.
[0026]
An endoscope apparatus according to a sixth aspect is the signal processing apparatus according to the fifth aspect, wherein the exposure time setting means instructs a color balance setting of an image displayed on the display device. The exposure time is set for each wavelength band based on the video signal output from the imaging device based on the above.
[0027]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
(Embodiment)
1 to 10 relate to an embodiment of the present invention, FIG. 1 is a block diagram showing a schematic configuration of an endoscope apparatus, FIG. 2 is a plan view showing a configuration of a rotary filter plate, and FIG. 3 is a charge coupled device type. FIG. 4 is a graph showing the spectral characteristics of the outer peripheral filter, FIG. 5 is a graph showing the spectral characteristics of the inner peripheral filter, and FIG. 6 is the transmission through the excitation light cut filter. FIG. 7 is a block diagram showing a color balance correction circuit, FIG. 8 is a flowchart showing processing when the color balance setting switch is pressed, and FIG. 9 is a timing chart showing CCD received light amount and charge sweeping signal. FIG. 10 is a timing chart showing the input image signal and the color tone adjustment coefficient.
[0028]
(Constitution)
As shown in FIG. 1, the electronic endoscope apparatus 1 according to the present embodiment includes an electronic endoscope 2, a signal processing device 3, a light source device 5, and a monitor 6.
[0029]
The electronic endoscope 2 includes an elongated insertion portion 11 that can be inserted into a body cavity. A CCD 20 is built in the distal end portion 16 of the insertion portion 11.
[0030]
The electronic endoscope 2 is detachably connected to the signal processing device 3. The signal processing device 3 performs signal processing of the image signal obtained by the CCD 20.
[0031]
The light source device 5 is for emitting observation light. In the present embodiment, the light source device 5 and the signal processing device 3 are provided separately. The light source device 5 may be configured to be built in the signal processing device 3.
[0032]
The monitor 6 is connected to the signal processing device 3 and displays a video signal image-processed by the signal processing device 3.
[0033]
Next, the electronic endoscope 2 will be described in detail.
The electronic endoscope 2 has an elongated insertion portion 11 to be inserted into a patient body cavity.
Here, the insertion portion 11 is composed of a flexible portion in the case of the digestive tract, bronchi, head and neck (for pharynx) and bladder, and is composed of a rigid portion in the case of the abdominal cavity, thoracic cavity and uterus. .
[0034]
Inside the insertion portion 11, a light guide 12, a charge sweep signal line 13, and CCD output signal lines 14 and 15 are disposed.
[0035]
The distal end portion 16 of the insertion portion 11 is provided with the distal end side of the light guide 12, an illumination lens 17, an objective lens 18, an excitation light cut filter 19, and a CCD 20.
[0036]
The light guide fiber 12 guides the illumination light from the light source device 5 provided in the signal processing device 3 to the distal end portion 16 of the insertion portion 11.
[0037]
The illumination lens 17 is mounted on the distal end portion 16 of the insertion portion 11 and is disposed on the distal end surface side of the light guide fiber 12.
[0038]
The illumination light guided from the light source device 5 by the light guide fiber 12 is irradiated to the subject 7 through the illumination lens 17.
[0039]
The objective lens 18 is for imaging light from the subject 7.
The excitation light cut filter 19 is mounted on the front surface of the CCD 20 and removes excitation light by blocking light having a wavelength of 460 nm or less. That is, the excitation light cut filter 19 has a spectral characteristic that transmits autofluorescence (approximately 500 nm or more) generated from living tissue and does not transmit excitation light.
[0040]
Reflected light and autofluorescence from the subject 7 form an image on the light receiving area 70 (see FIG. 3) of the CCD 20 via the objective lens 18 and the excitation light cut filter 19.
[0041]
The CCD 20 is an image sensor provided at the distal end portion 16 of the insertion portion 11 and disposed at the imaging position of the objective lens 18.
[0042]
In this embodiment, the CCD 20 is arranged in a direct view, but the CCD 20 can be arranged in a perspective view or a side view.
[0043]
The CCD 20 is connected to an exposure time control circuit 43 in the signal processing device 3 through a charge sweeping signal line 13. The CCD 20 performs electronic shutter control based on the charge sweeping signal generated by the exposure time control circuit 43.
[0044]
Further, the CCD 20 performs signal charge accumulation, sensitivity control, and readout by a drive signal from a CCD drive circuit (not shown).
[0045]
The subject image formed in the light receiving area 70 (see FIG. 3) of the CCD 20 by the objective lens 18 and the excitation light cut filter 19 is transferred after being photoelectrically converted by each pixel of the CCD 20 and output. The output signal from the CCD 20 is supplied to preprocess circuits 31 and 32 in the signal processing device 3 via CCD output signal lines 14 and 15, respectively.
[0046]
In addition, the electronic endoscope 2 has a filter changeover switch 21 mounted on the operation unit on the proximal end side. The filter changeover switch 21 is for instructing the changeover of the filter.
[0047]
The operation signal of the filter changeover switch 21 is supplied to the CPU 40 in the signal processing device 3.
[0048]
The signal processing apparatus 3 includes preprocessing circuits 31 and 32, analog / digital conversion circuits (hereinafter referred to as A / D conversion circuits) 33 and 34, color balance correction circuits 35 and 36, and a multiplexer 37. Memory 38R, 38G, 38B, digital / analog conversion circuit (hereinafter referred to as D / A conversion circuit) 39R, 39G, 39B, CPU 40, sampling circuit 41, color balance setting switch 42, and exposure time control circuit 43.
[0049]
Here, the CCD output signal line 14, the preprocess circuit 31, the A / D conversion circuit 33, and the color balance correction circuit 35 process the signal from the A channel for processing the signal from the odd line 71 in the light receiving area 70 shown in FIG. It is a system.
[0050]
The CCD output signal line 15, the preprocess circuit 32, the A / D conversion circuit 34, and the color balance correction circuit 36 shown in FIG. 1 are B channel signals for processing signals from the even lines 72 in the light receiving area 70 shown in FIG. It is a processing system.
[0051]
As shown in FIG. 1, the signal processing apparatus 3 includes preprocess circuits 31 and 32, A / D conversion circuits 33 and 34, color balance correction circuits 35 and 36, a multiplexer 37, and synchronization memories 38R, 38G, and 38B. The video signals flow in the order of the D / A conversion circuits 39R, 39G, and 39B.
[0052]
A signal after A / D conversion by the A / D conversion circuits 33 and 34 is input to the sampling circuit 41.
[0053]
The light source device 5 includes a xenon lamp (hereinafter referred to as a lamp) 51, an infrared cut filter 52, a rotary filter plate 53, motors 54 and 55, and a condenser lens 56.
[0054]
The lamp 51 emits illumination light. The infrared cut filter 52 is provided on the illumination optical path of the lamp 51 and limits the transmission wavelength. The motor 54 drives the rotary filter plate 53 to rotate. The motor 55 is for moving the rotary filter plate 53 in a direction perpendicular to the optical axis.
[0055]
As shown in FIG. 2, the rotary filter plate 53 has a double structure in which filter sets 58 and 59 are arranged on the outer peripheral portion and the inner peripheral portion, respectively.
[0056]
On the outer periphery of the rotary filter plate 53, an R filter 61R, a G filter 61G, and a B filter 61B that transmit light of red (R), green (G), and blue (B) wavelengths are arranged.
[0057]
That is, the R filter 61R, the G filter 61G, and the B filter 61B constitute an outer peripheral filter set 58.
[0058]
On the inner periphery of the rotary filter plate 53, a G ′ filter 62 that transmits narrow band light of 540 to 560 nm, an excitation filter 63 that transmits excitation light of 390 to 450 nm, and an R ′ that transmits narrow band light of 600 to 620 nm. A filter 64 is arranged.
[0059]
That is, the G ′ filter 62, the excitation filter 63, and the R ′ filter 64 constitute an inner peripheral filter set 59.
[0060]
Further, the portion of the rotary filter plate 53 other than where the filters are arranged is formed by a member 65 that blocks light.
[0061]
Next, the spectral characteristics of the outer and inner filters of the rotary filter plate 53 will be described with reference to FIGS. 4 and 5.
[0062]
As shown in FIG. 4, the outer R filter 61R, G filter 61G, and B filter 61B have a spectral distribution with no gap between the transmission spectra.
[0063]
As shown in FIG. 5, the G ′ filter 62, the excitation filter 63, and the R ′ filter 64 on the inner periphery have a discrete spectral distribution with a gap between each transmission spectrum.
[0064]
As illustrated in FIG. 3, the CCD 20 includes a light receiving area 70, horizontal transfer channels 73 and 74, transfer channels 75 and 76 with CMD (Charge Multiplexing Device), and charge detection units 77 and 78.
[0065]
The CMD-attached transfer channels 75 and 76 are composed of a plurality of cells having approximately the same number of cells as the horizontal transfer channels 73 and 74.
[0066]
The signal charges generated in each pixel in the light receiving area 70 are read out on the two channels A and B separately on the odd line 71 and the even line 72 by the vertical transfer pulse.
[0067]
The signal charges read from the odd-numbered lines 71 and the even-numbered lines 72 are transferred to the horizontal transfer channels 73 and 74 for each horizontal line, and are transferred from the horizontal transfer channels 73 and 74 to the transfer channels 75 with CMD by the horizontal transfer pulses, respectively. 76. In the transfer channels with CMD 75 and 76, the signal charge is amplified by applying the sensitivity control pulse while the signal charge is transferred through each cell by the horizontal transfer pulse. Therefore, every time signal charges are transferred through the cells of the transfer channel with CMD, the amplification factor increases in a geometric series. The amplified signal charges are sequentially transferred to the charge detectors 77 and 78. The charge detectors 77 and 78 convert the charges from the CMD-attached transfer channels 75 and 76 into voltages and output them to the CCD output signal lines 14 and 15, respectively.
[0068]
With such a configuration, the CCD 20 has a CMD arranged in a horizontal register, and can be variably amplified by an external sensitivity control pulse.
[0069]
As shown in FIG. 6, the excitation light cut filter 19 shown in FIG. 1 has a cutoff-type transmission characteristic that blocks light having a wavelength of 460 nm or less.
[0070]
The color balance correction circuit 35 shown in FIG. 1 has a color tone adjustment coefficient storage memory 81 and a digital multiplier 82 as shown in FIG.
[0071]
The color adjustment coefficient storage memory 81 rewrites the color adjustment coefficient based on the memory rewrite signal from the CPU 40, and guides the data of the color adjustment coefficient to one input terminal of the digital multiplier 82.
[0072]
An input image signal from the A / D conversion circuit 33 is led to the other input terminal of the digital multiplier 82.
[0073]
The digital multiplier 82 multiplies the input image signal from the A / D conversion circuit 33 by the color tone adjustment coefficient in the color tone adjustment coefficient storage memory 81 and outputs the result to one input terminal of the multiplexer 37.
[0074]
Further, the color balance correction circuit 36 shown in FIG. 1 has only the input / output changed to the other input terminal of the A / D conversion circuit 34 and the multiplexer 37, and the other configuration is the color balance correction circuit shown in FIG. This is the same as the circuit 35.
[0075]
(Function)
The operation of this embodiment will be described below.
In FIG. 1, light for illuminating the subject 7 is emitted from the lamp 51 of the light source device 5. The light emitted from the lamp 51 passes through the infrared cut filter 52, the rotary filter plate 53 and the condenser lens 56 and enters the light guide fiber 12 of the electronic endoscope 2.
[0076]
In this case, the infrared cut filter 52 cuts infrared light and prevents unnecessary heat and light from being irradiated to each filter on the rotary filter plate 53.
[0077]
The rotating filter plate 53 has an outer filter set 58 arranged on the optical path during normal observation, and is driven to rotate at a predetermined speed by the motor 54 so that the R filter 61R, G filter 61G, and B filter 61B are on the optical path. They are sequentially arranged to transmit red, green and blue light respectively. Thereby, red light, green light, and blue light are sequentially emitted from the light source device 5 during normal observation.
[0078]
During fluorescence observation, the motor 55 moves the rotary filter plate 53 in a direction perpendicular to the optical axis in accordance with a signal from a filter position control circuit (not shown). Thereby, the filter set 59 on the inner periphery of the rotary filter plate 53 is inserted on the optical axis.
[0079]
When the inner peripheral filter set 59 is inserted, the rotary filter plate 53 is rotationally driven by the motor 54 at a predetermined speed with the G ′ filter 62, the excitation filter 63, and the R ′ filter 64 being disposed on the optical path. Accordingly, the light source device 5 sequentially emits light having wavelengths of 540 to 560 nm, 390 to 450 nm, and 600 to 620 nm.
[0080]
Here, light of 390 to 450 nm is excitation light for exciting autofluorescence from living tissue.
[0081]
The light incident on the light guide fiber 12 of the electronic endoscope 2 is irradiated to the subject 7 such as the digestive tract via the illumination lens 17 at the distal end portion 16 of the insertion portion 11.
[0082]
Light scattered, reflected, and radiated from the subject 7 is imaged and imaged on the light receiving area 70 (see FIG. 3) of the CCD 20 via the objective lens 18 of the distal end portion 16.
[0083]
Here, the excitation light cut filter 19 extracts the fluorescence by blocking the excitation light of 390 to 450 nm on the front surface of the CCD 20.
[0084]
The CCD 20 is driven by a CCD drive circuit (not shown) in synchronization with the rotation of the rotary filter plate 53, and corresponds to the irradiation light transmitted through the filters of the rotary filter plate 53 such as the R filter 61R, the G filter 61G, and the B filter 61B. The image signals to be output are sequentially output to the signal processing device 3. The image signals sequentially output to the signal processing device 3 are two systems, that is, the A channel corresponding to the odd line 71 and the B channel corresponding to the even line 72.
[0085]
In the CCD 20, if necessary, sensitivity control pulses from a sensitivity control pulse generation circuit (not shown) are input to the transfer channels 75 and 76 with CMD, thereby generating secondary electrons by impact ionization to generate signal charges. Amplify. The amplification factor here is controlled by the amplitude of the sensitivity control pulse.
[0086]
The A-channel and B-channel image signals input to the signal processing device 3 are first input to the preprocess circuits 31 and 32, respectively. The preprocess circuits 31 and 32 take out appropriate A channel and B channel image signals by processing such as CDS (correlated double sampling).
[0087]
The A channel and B channel image signals output from the preprocess circuits 31 and 32 are converted from analog signals to digital signals by A / D conversion circuits 33 and 34, respectively.
[0088]
The digital signals of the A channel and B channel images output from the A / D conversion circuits 33 and 34 are input to the color balance correction circuits 35 and 36, respectively.
[0089]
A color tone adjustment unit is written in the color tone adjustment coefficient storage memory 81 of the color balance correction circuits 35 and 36 by the CPU 40. The color balance correction circuits 35 and 36 input the input signals for each irradiation wavelength based on a color discrimination signal (not shown). Amplify at a predetermined magnification.
[0090]
The multiplexer 37 combines the digital signals of the A channel and B channel images from the color balance correction circuits 35 and 36 into a digital image signal of one system, and also converts the digital signal of the frame sequential image to R (or narrowband green). ), G (or fluorescence), and B (or narrowband red reflected light) are branched and output to the synchronization memories 38R, 38G, and 38B, respectively.
[0091]
In the simultaneous memories 38R, 38G, and 38B, the sequential images are synchronized by simultaneously reading the sequentially stored images. The synchronized digital signals in the respective wavelength bands of R, G, B are subjected to conversion for correcting the gamma characteristics of the monitor in a gamma correction circuit (not shown), and D / A conversion circuits 39R, 39G, 39B, respectively. Is converted into an analog signal and displayed on the monitor 6.
[0092]
During normal light observation, red reflected light, green reflected light, and blue reflected light components are displayed on the RGB pixels of the monitor 6, respectively.
[0093]
During fluorescence observation, narrow band green reflected light, fluorescence, and narrow band red reflected light are displayed on the RGB pixels of the monitor 6, respectively.
[0094]
On the other hand, the exposure time control circuit 43 controls the exposure amount in the CCD 20 by sending a charge sweeping signal to the CCD 20. The charge sweeping timing by the exposure time control circuit 43 is adjusted for each irradiation wavelength of illumination light.
[0095]
In addition, when the filter changeover switch 21 is pushed by the operator, the CPU 40 recognizes this, and the motor 40 is driven by the CPU 40 to switch the filter set 58 on the outer periphery of the rotary filter plate 53 and the filter set 59 on the inner periphery. , Normal observation and fluorescence observation are switched.
[0096]
Simultaneously with this switching, the CPU 40 switches various settings in the signal processing device 3 between normal observation and fluorescence observation.
[0097]
When the operator of the electronic endoscope apparatus 1 adjusts the color balance during normal observation, the color balance setting is started by pressing the color balance setting switch 42 in a state where the white reference object is imaged.
[0098]
Next, processing when the color balance setting switch 42 is pressed will be described with reference to FIG.
[0099]
As shown in FIG. 8, when the color balance setting switch is pressed in the normal light observation mode, first, in step S1, the CPU 40 sets the maximum exposure time as a provisional exposure time to the exposure time control circuit 43 for all the RGB colors. It gives to the image signal of the wavelength band. That is, the exposure time control circuit 43 stops the function of the electronic shutter of the CCD 20. As a result, the received light amounts of the RGB colors of the CCD 20 are as shown in FIG.
[0100]
Next, CPU40 acquires the brightness of the image sampled by the sampling circuit 41 with respect to each RGB in step S2.
[0101]
Next, in step S3, the CPU 40 calculates an appropriate exposure time based on the sampling data of the A channel. Here, since the purpose is to set an approximate color balance, assuming that the sampling values of the RGB images are Vr, Vg, and Vb, the RGB color is such that the ratio is 1 / Vr: 1 / Vg: 1 / Vb. The exposure time is calculated. At this time, in order to ensure brightness, it is preferable not to use the electronic shutter of the CCD 20 when the exposure time in RGB is the maximum.
[0102]
Next, the CPU 40 outputs the exposure time calculated in step S3 to the exposure time control circuit 43 in step S4. Thereby, the exposure time control circuit 43 sends a charge sweeping signal shown in FIG. 9B to the CCD 20 so that the calculated exposure time is reached. Even if the exposure time is set in this way, there is a low possibility that the color balance is completely at a desired ratio for the reason described with reference to FIGS.
[0103]
Next, in step S5, the CPU 40 acquires RGB values sampled by the sampling circuit 41 again in order to perform accurate color balance adjustment and AB channel adjustment.
[0104]
Next, in step S6, the CPU 40 calculates a color tone adjustment coefficient to be set in the color balance correction circuits 35 and 36. Here, assuming that the sampling values of the RGB images are Vr ′, Vg ′, and Vb ′, the color tone adjustment coefficient is set so that the amplification factor ratio of RGB becomes 1 / Vr ′: 1 / Vg ′: 1 / Vb ′. calculate.
[0105]
Next, in step S7, the CPU 40 stores the tone adjustment coefficient calculated in step S6 in a separate area for each observation mode and for each RGB in the tone adjustment coefficient storage memory 81 shown in FIG. Thereby, the color balance setting is completed.
[0106]
By such processing, the color balance correction circuit 35 performs more strict correction on the color balance that is generally corrected by the exposure time control.
[0107]
Thereafter, when normal electronic imaging is performed by the electronic endoscope apparatus 1, the color balance correction circuit 35 is stored in a separate area for each observation mode and for each RGB in the tone adjustment coefficient storage memory 81 in FIG. 10) and the input image signal shown in FIG. 10A from the A / D conversion circuit 33 imaged in accordance with the observation mode and the rotation of the rotary filter 53 are integrated by the digital multiplier 82. As a result, the RGB image signals subjected to strict color balance correction are amplified by the amplification factor ratio and output from the color balance correction circuit 35.
[0108]
For the B channel color balance correction circuit 36, in addition to the color balance adjustment, the tone correction coefficient is calculated so as to cancel the inter-channel variation with the A channel. Other operations of the B channel color balance correction circuit 36 are the same as those of the A channel color balance correction circuit 35.
[0109]
When the operator of the electronic endoscope apparatus 1 adjusts the color balance during the fluorescence observation, the operator inserts the insertion portion 11 into the body and presses the color balance switch 22 in a state where the normal mucous membrane of the patient is imaged in the fluorescence observation mode. Color balance setting starts. The subsequent operation is the same as in normal observation.
[0110]
The electronic endoscope 2 includes an imaging device (CCD 20) that images the subject 7 for each wavelength band of irradiated illumination light.
[0111]
The color balance correction circuits 35 and 36 are amplification means for amplifying a signal corresponding to the subject 7 output from the CCD 20 for each wavelength band.
[0112]
The exposure time control circuit 43 is an exposure time setting means for setting the exposure time of the CCD 20 for each wavelength band.
[0113]
Further, the CPU 40 sets the amplification factors of the color balance correction circuits 35 and 36 for each wavelength band based on a signal corresponding to the subject 7 imaged by the CCD 20 with the exposure time set by the exposure time setting means. It is an amplification factor setting means.
[0114]
The monitor 6 is a display device for color-displaying an image corresponding to the signal amplified by the color balance correction circuits 35 and 36.
[0115]
The color balance setting switch 42 is color balance setting instruction means for instructing the color balance adjustment of the image displayed on the monitor 6.
[0116]
The exposure time setting means sets the exposure time for each wavelength band based on the video signal output from the CCD 20 based on an instruction from the color balance setting switch 42.
[0117]
(effect)
According to such an embodiment, since the color balance is corrected by exposure time control, it is not necessary to amplify only a specific color with a high amplification factor, and the influence of noise on any color component is reduced. can do. Further, since the amplification factor control is also used for correcting the color balance, a slight color balance error after the exposure time control can be corrected, and the color balance can be set more accurately. This makes it possible to obtain a better image with less noise under an accurately set color balance.
[0118]
Further, according to the present embodiment, since the exposure time is set based on the instruction of the color balance setting switch 42 as the color balance setting instruction means, all the colors are controlled regardless of the fluctuation at the time of manufacturing the optical filter. As a result, the amplification factor becomes almost equal, and the influence of noise on any color component can be made very small.
[0119]
Further, the present embodiment has a particularly remarkable effect in terms of suppressing the influence of noise by being applied to the fluorescent electronic endoscope apparatus 1 that is likely to generate noise due to the fluctuation of the optical filter.
[0120]
Furthermore, the present embodiment is applied to the electronic endoscope apparatus 1 that emits illumination light having a discrete spectral distribution shown in FIG. It has a particularly remarkable effect in terms of suppression.
[0121]
In this embodiment, the present invention is applied to the electronic endoscope apparatus 1 capable of observing the fluorescence in the visible region. However, the narrow band discrete three wavelengths as disclosed in JP-A-2002-95635 are used. It can also be applied to reflected light observation, infrared light observation, and fluorescence observation in the infrared band.
[0122]
Further, in this embodiment, amplification for adjusting the color balance is performed inside the signal processing device 3, but it may be amplified by the transfer channels 75 and 76 with CMD inside the CCD 20.
[0123]
Further, the ratio of the color to be adjusted is not limited to 1: 1: 1. For example, even when the normal mucosa is displayed in a slightly greenish color during fluorescence observation, it is effective in recognizing the lesion.
[0124]
In addition, the calculation of exposure time is not limited to a method that simply assumes the linearity between exposure time and exposure amount, but increasing the accuracy by approximating to other functions is also effective in suppressing noise. It is.
[0125]
In addition, the color balance setting switch is not limited to that provided in the main body of the signal processing apparatus, and may be provided in the operation unit of the electronic endoscope 2 or may be a foot switch that is stepped on with a foot.
[0126]
[Appendix]
According to the above-described embodiment of the present invention described in detail above, the following configuration can be obtained.
[0127]
(Additional Item 1) Illumination light supply means for sequentially supplying light of different wavelength bands to irradiate a subject;
Imaging means for sequentially imaging a subject for each wavelength band;
Amplifying means for amplifying the signal imaged by the imaging means;
A display device for color-displaying the signal amplified by the amplification means;
Exposure time setting means for setting the exposure time of the imaging means for each wavelength band;
An electronic endoscope apparatus comprising: an amplification factor setting unit configured to set an amplification factor for each wavelength band in the amplification unit based on a signal output from the imaging unit after the exposure time is set.
[0128]
(Additional Item 2) Color balance setting instruction means for instructing the balance setting of the color displayed on the display device,
The electronic apparatus according to claim 1, wherein the exposure time setting unit sets an exposure time for each wavelength band based on a signal output from the imaging unit in accordance with an instruction from the color balance setting instruction unit. Endoscopic device.
[0129]
(Additional Item 3) The light source means emits light having a wavelength for exciting the subject,
3. The electronic endoscope apparatus according to appendix 1 or 2, wherein the imaging means images fluorescence from a subject.
[0130]
(Additional Item 4) The electronic endoscope apparatus according to Additional Item 1 or 2, wherein the different wavelength bands have a discrete spectral distribution.
[0131]
(Additional Item 5) The electronic endoscope apparatus according to any one of Additional Items 1 to 4, wherein the exposure time setting unit sets an exposure time by an electronic shutter.
[0132]
(Additional Item 6) The electronic endoscope apparatus according to Additional Item 5, wherein at least one of the exposure times set for each wavelength band is an exposure time obtained by stopping the electronic shutter.
[0133]
(Additional Item 7) A color balance adjustment method for an electronic endoscopic forging apparatus that sequentially irradiates a subject with illumination light having different wavelength bands and images the subject for each wavelength band of the illuminated illumination light,
Imaging a subject for each wavelength band based on a predetermined exposure time;
Setting the exposure time for each wavelength band based on the brightness of the image signal corresponding to the subject image for each wavelength band;
Imaging a subject based on an exposure time for each set wavelength band;
Calculating the amplification factor of the image signal for each wavelength band based on the brightness for each wavelength band of the image signal corresponding to the subject imaged based on the set exposure time;
Amplifying the image signal for each wavelength band based on the calculated amplification factor;
A method for adjusting the color balance of an electronic endoscope apparatus, comprising:
[0134]
As described above, according to the present invention, it is possible to obtain a better image with less noise under an accurately set color balance.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a schematic configuration of an electronic endoscope apparatus according to an embodiment of the present invention.
FIG. 2 is a plan view showing a configuration of a rotary filter plate according to an embodiment of the present invention.
FIG. 3 is a block diagram of a CCD according to the embodiment of the present invention.
FIG. 4 is a graph showing spectral characteristics of an outer peripheral filter according to an embodiment of the present invention.
FIG. 5 is a graph showing spectral characteristics of an inner filter according to an embodiment of the present invention.
FIG. 6 is a graph showing transmission characteristics of the excitation light cut filter according to the embodiment of the present invention.
FIG. 7 is a block diagram showing a color balance correction circuit according to the embodiment of the present invention.
FIG. 8 is a flowchart showing processing when a color balance setting switch according to an embodiment of the present invention is pressed.
FIG. 9 is a timing chart showing a CCD light reception amount and a charge sweep signal according to the embodiment of the present invention.
FIG. 10 is a timing chart showing an input image signal and a color tone adjustment coefficient according to the embodiment of the present invention.
FIG. 11 is a graph showing the relationship between the exposure amount of a conventional rotary filter and time.
FIG. 12 is a graph showing the relationship between the exposure amount and the exposure time of a conventional rotary filter.
[Explanation of symbols]
1 ... Electronic endoscope device
2 ... Electronic endoscope
3 ... Signal processing device
5 ... Light source device
6 ... Monitor
11 ... Insertion part
20 ... CCD
21 ... Filter changeover switch
31, 32 ... Pre-processing circuit
33, 34 ... A / D conversion circuit
35, 36 ... Color balance correction circuit
37 ... Multiplexer
38R, 38G, 38B ... Simultaneous memory
39R, 39G, 39B ... D / A conversion circuit
40 ... CPU
41. Sampling circuit
42 ... Color balance setting switch
43 ... Exposure time control circuit
51 ... Xenon lamp
53 ... Rotating filter plate
54, 55 ... motor
61R ... R filter
61G ... G filter
61B ... B filter
62 ... G 'filter
63 ... Excitation filter
64 ... R 'filter

Claims (6)

A light source device that sequentially irradiates illumination light having different wavelength bands to a subject;
An endoscope provided with an imaging device for imaging the subject for each wavelength band of irradiated illumination light;
Amplifying means for amplifying a signal corresponding to a subject output from the imaging device for each wavelength band;
Exposure time setting means for setting the exposure time of the imaging device for each wavelength band;
An amplification factor setting unit that sets the amplification factor of the amplification unit for each wavelength band based on a signal corresponding to the subject imaged by the imaging device with the exposure time set by the exposure time setting unit;
An electronic endoscope apparatus comprising: A display device for color-displaying an image corresponding to the signal amplified by the amplification means;
Color balance setting instruction means for instructing color balance adjustment of video displayed on the display device;
Further comprising
2. The exposure time setting unit according to claim 1, wherein the exposure time setting unit sets an exposure time for each wavelength band based on a video signal output from the imaging apparatus based on an instruction from the color balance setting instruction unit. Electronic endoscope device. The light source device supplies excitation light for exciting the subject to the subject,
The electronic endoscope apparatus according to claim 1, wherein the imaging apparatus images fluorescence from a subject. The electronic endoscope apparatus according to claim 1, wherein the light source device supplies illumination light in a wavelength band having a discrete spectral distribution to a subject. A signal processing device for processing a signal corresponding to a subject output from an endoscope provided with an imaging device,
Amplifying means for amplifying a signal corresponding to the subject imaged by the imaging device for each wavelength band of illumination light sequentially irradiated to the subject and having a different wavelength band for each wavelength band;
Exposure time setting means for setting the exposure time of the imaging device for each wavelength band;
An amplification factor setting means for setting the amplification factor of the amplification unit for each wavelength band based on a signal corresponding to the subject imaged by the imaging device with the exposure time set by the exposure time setting unit;
A signal processing apparatus comprising: The exposure time setting means sets an exposure time for each wavelength band based on a video signal output from the imaging device based on a color balance setting instruction for instructing a color balance of a video displayed on a display device. The signal processing apparatus according to claim 5.

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